The southern group of islands include Sumba, Timor and Babar. They are not volcanic and are probably part of the Australian plate.[3]

Since colonial times in Indonesia, people have been studying the geographical history of the islands. However, we still do not fully understand how the islands were formed. Ideas of how the islands were formed changed in many ways during the last decades of the 20th century.[4]

At the point where two tectonic plates collide, the Lesser Sunda Islands are some of the most geologically complex and active regions in the world.[4] There are several volcanoes located on the Lesser Sunda Islands.[5]

The English used in this section or section may not be easy for everybody to understand. You can help Wikipedia by reading Wikipedia:How to write Simple English pages, then simplifying the article.(November 2013)An editor's reason for this is: Not simplified enough from the enwiki article.

The Lesser Sunda Islands are different from the large islands of Java or Sumatra because it is made of many small islands. These small islands are sometimes divided by deep oceanic trenches. Because flora and fauna cannot move between the islands easily, there are many localised species like the Komodo dragon because of evolution.[4] In The Malay Archipelago, Alfred Wallace writes about the "Wallace Line" that passes between Bali and Lombok, along the deep waters of the Lombok Strait. In this imaginary line between Bali and Lombok, even when sea levels were lower, the sea stopped flora and fauna from moving between islands. The islands east of the Lombok Strait are part of Wallacea, and have wildlife of Asian and Australasianorigin in this region.[6] In the Lesser Sundas, there are many plants and animals that come from Asia, because Weber's Line, which separates the parts of Wallacea that have both Asian and Australasian species, is east of the Lesser Sundas. These islands have the driest climate in Indonesia.

Some of the islands east of the Wallace line, from Lombok and Sumbawa east to Flores and Alor, have original vegetation of dry forest and not the rain forest that covers most parts of Indonesia. These islands have been designated by the World Wildlife Fund as the Lesser Sundas deciduous forests ecoregion.[7] The higher slopes of the islands contain forests of tall Podocarpus conifers and Engelhardias with an undergrowth of lianas, epiphytes, and orchids such as Corybas, Corymborkis, and Malaxis (Adder's Mouth). The islands' coastal plains used to be savanna grasses like the savanna with Borassus flabellifer palm trees on the coasts of Komodo, Rincah and Flores. While most of the vegetation on these islands is dry forest there are small areas of rainforest on these islands too, especially in lowland areas and riverbanks on Komodo. There is also a special area of dry thorny forest on the southeast coast of Lombok. Thorn trees used to be more common in coastal areas of the islands but have mostly been cleared.

More than half of the original vegetation of the islands are cleared. This is because people cleared the forest to grow food, like rice, for settlements or because there were forest fires. Only Sumbawa now contains a large area of intact natural forest, while Komodo, Rincah and Padar are now protected as Komodo National Park.

General observations[8] about small islands that can be applied to Nusa Tenggara include:[9]

A larger amount of the landmass will be affected by volcanic activity, earthquakes, landslips, and cyclone damage;

↑Beller, W., P. d'Ayala, and P. Hein. 1990. Sustainable development and environmental management of small islands. Paris and New Jersey: United Nations Educational, Scientific, and Cultural Organisation and Parthenon Publishing Group Inc.; Hess, A, 1990. Overview: sustainable development and environmental management of small islands. In Sustainable development and environmental management of small islands. eds W. Beller, P. d'Ayala, and P. Hein, Paris and New Jersey: United Nations Educational, Scientific, and Cultural Organisation and Parthenon Publishing Group Inc. (both cited in Monk)